A visa is a document, normally affixed within the passport, allowing the bearer or alien to apply for entry into the country in question. It does not however automatically guarantee entry into that country. Other nations require visas for exit, but this depends on the country.
CLASSES OF VISA
Visas come in many forms, so it is important to obtain the visa appropriate for what you intend to do. Here are some of the most common varieties:
Tourist Visas are issued to persons wishing to travel to a country for sightseeing or vacation. Most tourist visas last for, at most, six months.
Transit Visas are issued to people passing through the country without a significant stay, normally for anywhere from 24 hours to ten days.
Business Visas are issued if one needs to conduct financial transactions in the country, sign contracts, attend training or meetings, and a whole plethora of work-related activities, but employment is prohibited.
Student Visas are issued to those who wish to undertake a course of study in another country. Proof of enrollment is necessary.
Work Visas are permits allowing one to hold a paid job in the destination country for a period of time. These are notoriously hard to acquire unless special arrangements exist between your home country and the destination country.
Working Holiday Visas are work visas that allow short-term jobs to be undertaken to subsidize a vacation.
Religious Pilgrimage Visas, such as visas given for the Hajj, entitle the bearer to visit a religious shrine or site. These are common in most Muslim countries.
Retirement Visas allow one to reside in a country indefinitely, so long as they abide by the law and don't seek paid employment.
Immigrant Visas permit one to resettle in a country.
ENTRY WITHOUT A VISA
Some countries permit certain nationalities to enter without an advance visa, but other conditions may apply for entry and the stay. For example, all nationalities in the European Union can generally freely travel from one country to another with almost no restrictions. The United States allows certain nationals to enter under the Visa Waiver Program for tourism and business only, provided they fill out an online application prior to their arrival.
Some countries still do not require transit visas for transits of certain lengths, such as Saudi Arabia and China.
If your country lets a nationality in without a visa, don't automatically assume that you won't need one, especially if you are planning to stay for extended periods (i.e. to work, study or immigrate either temporarily or permanently). Check to make certain of your status before entry.
OBTAINING VISA
Some countries, such as Cambodia and Turkey, offer provisions for a visa on arrival. This normally involves submitting an application at the border and paying a nominal fee. Others, such as Armenia, Cambodia, and Australia, offer an electronic visa service where you can apply online, oft for a nominal fee.
If your target destination does not offer this, then it's time to contact the consulate. Figure out what is needed to apply for said visa.
For most countries, begin the process at least four weeks prior to your trip. This will ensure that you can complete all of the necessary work in advance of when you desire to leave. Some countries allow for quicker turnaround times, but this comes with the obvious risk of missing your flight or paying a substantially higher fee.
Typically, a visa application package will consist of your passport with blank visa pages, the original and possibly several copies of the application form, relevant financial information (bank statements, medical insurance, etc.), photographs, vaccination information where necessary (mostly for yellow fever if you travel to an endemic region), hotel reservations/contact information for your host and plane ticket, an invitation when required (such as Algeria and Russia), and an application fee. Keep in mind that some countries reciprocate the visa fee, meaning that you pay what their citizens pay. Brazil and China are both known to do this, levying a US$130 fee for US citizens to apply for a visa to match what the US charges Brazilians and Chinese.
Typically, application fees are not refundable, even if your visa is denied.
Keep in mind that there are some countries where a trip to the consulate is highly advised, if not mandatory. The United States requires a consular interview, as does Germany.
It is also important to know the holidays of your country as well as the holidays of the country you wish to enter because the embassy or consulate of the latter will be closed on either country's holidays.
